Servo steering systems may be in the form of electrically assisted servo steering systems, also called EPAS (Electric Power Assisted Steering), or hydraulically assisted servo steering systems, also called HPAS (Hydraulic Power Assisted Steering). Electrically assisted servo steering systems normally have a higher friction level, that is to say a greater steering resistance, than hydraulically assisted servo steering systems. At low vehicle speeds, this results in a reduced capability to reset the steering wheel to the neutral position, in which the steering wheel steers the vehicle straight ahead. For this reason, an active resetting function may be implemented in the electrical servo steering, or in its controller, which generates an additional torque in order to reset the steering wheel to the straight-ahead position (neutral position). This resetting torque is based only on input values such as the vehicle speed and the steering wheel position. Therefore, the resetting torque has the same magnitude when the friction value is high and when it is low (the friction of the tires on the road surface). Particularly when the friction value is low, the resetting torque that is produced is greater than necessary, and results in an excessive resetting capability, and can also result in the vehicle driver having an undesirable, artificial steering sense, which may be disturbing to the vehicle driver.
There is a need for optimizing a method of resetting a steering wheel such that a resetting torque is made available for both high and low friction values.